The invention disclosed herein relates generally to mailing systems, and more particularly to a transport method and system for controlling the timing of articles being processed by a mailing system.
Mailing systems, such as, for example, a mailing machine, often include different modules that automate the processes of producing articles, such as, for example, mail pieces. Mail pieces can include, for example, envelopes, post cards, flats, and the like. The typical mailing machine includes a variety of different modules or sub-systems each of which performs a different task on the mail piece. The mail piece is conveyed downstream utilizing a transport mechanism, such as rollers or a belt, to each of the modules. Such modules could include, for example, a separating module, i.e., separating a stack of mail pieces such that the mail pieces are conveyed one at a time along the transport path, a moistening/sealing module, i.e., wetting and closing the glued flap of an envelope, a weighing module, and a metering/printing module, i.e., applying evidence of postage to the mail piece. The exact configuration of the mailing machine is, of course, particular to the needs of the user.
One indicator customers use to evaluate and measure the performance of mailing machines is overall mailing machine throughput. Conventionally, throughput is defined as the number of mail pieces processed per minute. Typically, customers desire to process as many mail pieces per minute as possible. There are several factors that can limit the throughput of a mailing system.
For example, the computation of an indicium for each mail piece being processed takes time to complete. Typically, a control device, such as, for example, a microprocessor, performs user interface and controller functions for the mailing machine. Specifically, the control device provides all user interfaces, executes control of the mailing machine and print operations, calculates postage for debit based upon rate tables, provides the conduit for the Postal Security Device (PSD) to transfer postage indicia to the printer, operates with peripherals for accounting, printing and weighing, and conducts communications with a data center for postage funds refill, software download, rates download, and market-oriented data capture. The control device, in conjunction with an embedded PSD, provides the system meter that satisfies U.S. and international postal regulations regarding closed system information-based indicia postage meters. The requirements for an indicium for a closed system postage meter are defined in the xe2x80x9cPerformance Criteria for Information-Based Indicia and Security Architecture for Closed IBI Postage Metering System (PCIBI-C), dated Jan. 12, 1999. A closed system is a system whose basic components are dedicated to the production of information-based indicia and related functions, similar to an existing, traditional postage meter. A closed system, which may be a proprietary device used alone or in conjunction with other closely related, specialized equipment, includes the indicia print mechanism. The indicium consists of a two-dimensional (2D) barcode and certain human-readable information. Some of the data included in the barcode includes, for example, the PSD manufacturer identification, PSD model identification, PSD serial number, values for the ascending and descending registers of the PSD, postage amount, and date of mailing. In addition, a digital signature is required to be created by the PSD for each mail piece and placed in the digital signature field of the barcode. Several types of digital signature algorithms are supported by the IBIP, including, for example, the Digital Signature Algorithm (DSA), the Rivest Shamir Adleman (RSA) Algorithm, and the Elliptic Curve Digital Signature Algorithm (ECDSA).
Thus, for each mail piece the PSD must generate the indicium once the relevant data needed for the indicium generation is passed into the PSD and compute the digital signature to be included in the indicium. The generation of the indicia and computation of the digital signature requires a predetermined amount of time. For smaller mailing machines that do not have high throughput, the time delay associated with such generation and computation does not limit the throughput, i.e., the calculations are performed quickly enough and therefore are not a limiting factor for the throughput. For larger mailing machines with higher throughputs, however, the speed of processing the mail pieces may be limited by the time required for the PSD to perform its calculations in generating the digital signature and the indicium. Accordingly, the throughput of the mailing machine is confined due to the calculating time required by the PSD.
Another factor that can limit the throughput of a mailing system is related to the moistening/sealing function performed by a mailing system. Typically, a moistening/sealing module includes a structure for deflecting a flap of a moving mail piece away from the mail piece""s body to enable the moistening and sealing process to occur. The deflecting structure typically includes a stripper blade that becomes inserted between the flap of the mail piece and the body of the mail piece as the mail piece traverses the transport deck of the mailing machine. Once the flap has been stripped, the moistening device moistens the glue line on the mail piece flap in preparation for sealing the mail piece. A contact moistening system generally deposits a moistening fluid, such as, for example, water or water with a biocide, onto the glue line on a flap of a mail piece by contacting the glue line with a wetted applicator. In contact systems, the wetted applicator typically consists of a contact media such as a brush, foam or felt. The applicator is in physical contact with a wick. The wick is generally a woven material, such as, for example, felt, or can also be a foam material. At least a portion of the wick is wetted with the moistening fluid from a reservoir. The moistening fluid is transferred from the wick to the applicator by physical contact pressure between the wick and applicator, thereby wetting the applicator. A stripped mail piece flap is guided between the wick and applicator, such that the applicator contacts the glue line on the flap of the mail piece, thereby transferring the moistening fluid to the flap to activate the glue. The flap is then closed and sealed, such as, for example, by passing the closed mail piece through a nip of a sealer roller to compress the mail piece and flap together, and the mail piece passed to the next module for continued processing.
Thus, since the moistening fluid is transferred from the applicator to the glue line of the mail piece flap as the mail piece flap passes between the applicator and wick, there must be sufficient time, referred to generally as replenishment time, between mail pieces to allow additional moistening fluid to be transferred from the wick to the applicator, thereby wetting the applicator, for moistening the subsequent mail piece. Insufficient replenishment time can result in an insufficient amount of moistening fluid being applied to the mail piece flaps, which can result in improper and inconsistent sealing of the mail pieces. To provide sufficient replenishment time, it is, therefore, necessary to provide a sufficient gap between mail pieces. Typically, the longer the mail piece, the greater the necessary replenishment time, which leads to a greater gap between mail pieces. As the gap size increases, the throughput of the mailing machine decreases.
Still another indicator customers use to evaluate and measure the performance of mailing machines is the ability to handle mail pieces of mixed sizes. This capability eliminates the need to presort the mail pieces into similar sized batches for processing. Since this presorting is often a manual task, a great deal of labor, time and expense is saved through mixed mail piece feeding. It is therefore necessary to provide a mailing system that can handle mixed mail while optimizing the throughput based on the processing time and replenishment constraints described above.
Some prior art systems seek to address these issues by feeding mail pieces at a fixed pitch. That is, the length of the mail piece plus its associated gap is always equal to a constant regardless of the size of the mail piece. Although these fixed pitch systems generally work well, they suffer from disadvantages and drawbacks. For example, the pitch must be set sufficiently large so as to accommodate the gap size required for moistening fluid applicator replenishment of the largest mail piece the system can process. However, as a result, when mail pieces shorter than the largest mail piece are being fed, the gap size is unnecessarily large and throughput efficiency is reduced.
Other prior art systems seek to address these issues by feeding mail pieces with a fixed gap regardless of the size of the mail piece. That is, the gap between mail pieces is constant regardless of the size of the mail pieces. Thus, in fixed gap systems, the pitch between subsequent mail pieces will vary depending upon the size of the first mail piece. Although these fixed gap systems generally work well, they also suffer from disadvantages and drawbacks. For example, the gap must be set sufficiently large so as to accommodate the size of the smallest mail piece while still providing the mailing system modules with a sufficient amount of time to perform its tasks, such as, for example, generation of an indicium. Thus, the size of the smallest mail piece taken along with the size of the gap cannot be so small so as to exceed the capabilities of the remainder of the mailing system. However, as a result, when larger articles are being fed, the constant gap may be unnecessarily large and throughput efficiency is reduced.
Still other prior art systems have addressed these issues by operating in a combination-of fixed pitch and fixed gap modes based on the determined length of the mail piece. Thus, if the mail piece is longer than a predetermined length, the mailing machine will operate in a fixed gap mode to allow sufficient replenishment time for the moistening fluid applicator, and if the mail piece is less than or equal to the predetermined length, the mailing machine will operate in a fixed pitch mode to allow sufficient time for generation of an indicium. While this type of system has worked well, there are still some limitations. For example, if the length of a mail piece exceeds the predetermined length, the gap between this mail piece and the next mail piece is still set to a fixed value regardless of the amount the length of the first mail piece exceeds the predetermined length. This fixed value is based on the moistening fluid applicator replenishment time required for the largest mail piece the system can process. Thus, for example, if the predetermined length is 9.5 inches, the gap is the same for a mail piece that is 10 inches long, 11 inches long, 12 inches long, or 13 inches long, even though the replenishment times required for each of these mail piece lengths is different and therefore require different size gaps.
Thus, there exists a need for a transport method and system that operates to feed mixed size mail pieces in singular fashion and adaptively controls the velocity of the mail pieces such that overall system performance is optimized.
The present invention alleviates the problems associated with the prior art and provides a transport method and system that operates to feed mixed size mail pieces in singular fashion and adaptively controls the velocity of the mail pieces such that overall system performance is optimized.
In accordance with the present invention, a mailing system is provided with a transport for transporting mail pieces through the mailing system. The length of a mail piece is measured and a desired gap time between the mail piece and a subsequent mail piece is calculated. The desired gap time is proportional to the measured length of the mail piece, and provides for optimal throughput while still being within the necessary functional constraints of the mailing machine. The gap time between the mail piece and the subsequent mail piece is measured, and a difference between the desired gap time and measured gap time is calculated. Based on the calculated gap time difference, the velocity of the subsequent mail piece is adaptively controlled to decrease the difference between the desired gap time and the measured gap time such that the measured gap time is adjusted to be approximately equal to the desired gap time, thereby optimizing throughput of the mailing system.
In accordance with one embodiment of the present invention, a dwell time during which the subsequent mail piece is transported at a selected dwell velocity is determined to correct the difference between the desired gap time and the measured gap time. The dwell velocity can be selected based upon the amount of difference between the desired gap time and measured gap time. The subsequent mail piece is transported at the selected dwell velocity for the determined dwell time, thereby decreasing the difference between the desired gap time and measured gap time. By controlling the measured gap time such that it is substantially equivalent to the desired gap time, the throughput efficiency of the mailing system can be optimized.
Therefore, it should now be apparent that the invention substantially achieves all the above aspects and advantages. Additional aspects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the aspects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.